Apparatus for treating material



VJune 7,l 1938.

W. RAISCH APPARATUS FOR TREATING MATERIAL' Filed Sept. 1l, 193

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Patented June 7, 1938 UNITED STATES APPARATUS FOR TREA'IVING MATERIAL William Raisch, New York, N. Y., as'signor to Underpinning tY Foundation Co., Inc., New York, N. Y., a corporation of New York Application September 11, 1936, .Serial No. 100,282 y 10` claims. (ci. 11o- 12) The present invention relates to the treatment of material including a step of burning or roasting, and more particularly to treatment in which moisture and volatile constituents are driven oi by heating in a preliminary stage of operation and the solid residue is roasted or burned.

The principal objects of the invention are to provide novel, advantageous and eflicient apparatuses and processes for effecting treatment of this kind. An important feature of the apparatus resides in providing a multiple-hearth furnace, in which the material is fed downwardly from hearth to hearth through outlets for said hearths, with material-feeding devices or valves at certain hearths to pass the material through the corresponding outlets while preventing the passage of gases. In this Way the zones of treatment, corresponding to the compartments over the. various hearthsmay be separated into groups of zones, between which there is no direct passage of gases, for example an uppermost drying group, an intermediate or central group and a lowermost deodorizing group. Correspondingly the furnace would include an uppermost drying section, a central burning section and a lo-wermost final combustion and deodorizing section.

Other features relate to the use of part of the combustion gases from theburning section to assist the drying operation in the drying section and the nal burning in the lowermost section, to the treatment of gases and vapors from the drying section in the lower section for final burning and deodorizing, and to the manner in which heat from one part is` utilized in another.

While applicable to Vthe treatment of various materials, the present invention is particularly adapted for the disposal of waste material such as sewage solids in the form of sludge or screenings having a high moisture content.

In carrying out the invention, especially as applied to the disposal of sewage solids, use may be made ofy a multiple-hearth furnace comprising vertically spaced hearths with outlets at the center of one and the periphery of the next and vice versa, and rabbling means comprising a hollow shaft and rabbling devices extending therefrom over the hearths and arranged so as to work the material to the outlets of the hearthsV with which they are associated.

For better control inv operation, the furnace may be divided into an 4uppermost; or drying section, a central or burning section and a lowermost or `deodorizing section. Such division of the furnace may be effected by selecting certain hearths and providing at their outlets devices or valves adapted to discharge material to the next lower hearths and at the same time to prevent the passage of gases through the corresponding outlets.

Preheated air is admitted to the burning section and hot gases drawn from this section are passed through the uppermost and drying section to dry the material preparatory to burning. The gases are cooled considerably in the drying zone and mixed with vapors and then passed to the lowermost or deodorizing zone. Not all of the hot gases are passed to the drying zone, the rest of them being passed to the lowermost or deodorizing section and serving to raise the temperature of the gases from the 'drying section. Tok assure complete combustionV of the gases, additional heating for the lowermost section may be provided, as by the use of one or more iuid fuel burners. The proportions of the vhot gases 'passing from the burning section to section. If desired, burners may be used in theV drying hearth and of course in the burning Zone. The gases may be discharged from the lowermost or deodorizing section in any suitable manner as by utilization of natural draft. Preferably, however, the draft or flow of gases through the furnace is established in any suitable manner, as by means including a suction fan connected with the outlet of the deodorizing section. There maybe a considerable quantity of heat in the gases-drawn from the deodorizing section and this may be 'recovered to a considerable extent, as by passing the gases through a wasteheat boiler installation.

Obviously the raising of temperature, to `produce burning in some parts, may be eiected by use of other kinds of auxiliary fuel. Also, if con; siderable readily combustible be mixed with the less combustible sewage solids, the amount of supplementary fuel to be used may be reduced substantially. In some cases such additional combustible material, such as ne coal or paper, may be mixed with the sewage solids in connection witha screening operation, or in a set- "tling tank, or in connectionrwith'dewatering theVv sludge by use of alter.V

Other objects,` features'and advantages vvill ap-Y I fpear upon consideration of the following descrip- Vtion and' of the /draWi/ngin which the Vligure isV pa-sectional elevation illustratingV an `rapparatus embodying a preferred form of the invention.v 'Y Referring to the drawing'the invention may be Y Yembodied in an Yappzuatusr including a ,multiple-'1 hearth furnace II)y having 'a topY I I,hearths I2 toV inclusive, and a peripheralY Wall 2| in whichY Vthe top'and hearths are supported. Material isY Y deposited on the uppermost hearth I2 Vthroughra hopper 22, and a chute'23 extending through the top' II of the furnace andprovidedf'vjvitha pivoted l U doorV or gate 24l normally l'eld in'lg'closedposition bymeans of a Weighted arm' 25.1;As soon as a` sufficient amount vof material, togoyercomethe counterbalancing action-ofv the arm 25, collects ony theidoor 24, the dooror gate'swings downwardlyY about its pi otalsupport and the/materialen the door falls tothe hearth-I2.

J In orderthat the matenal on each hearth may, in connectionk with agitation thereof, bebrought into a layerY-and-gradually fed downwardly to a lowerhearth orfout ofthe furnace f roIr the hearth 20 whichV forms the/bottom offthelfurn'ace, eachY a of thehearthsrl?, I 4,I 6, I8 and V2l) may be provided The agitation ofthe material on the hearths andthe movementv of Y the materialY towardthe Vdiscllarge openingsfor outlets Ymay be effected byVV providineerereaeh hearth elle er mererebblne devices 2`8`invthe5general ,fformof an armpro-V- gi.; ijecting'radiallyffromy'a holloypcentraljshaft. V29 Y 40 .ithat'passes through the centralpartsfof the cen-f Y with relatively little clearance, ees Seals Ybeing provided atl=these ypoints torprevent Ypassagefof `gases throughV theseY last-mentioned heartlisVV ad- 'jacent'the central1shafti2r95 Eachof therrabbling devices-28rfmayberprovidedwithaatseries of with 'a Chute; 3l equippeel'vlith.Y e' riveted gateY 0r dobrfurgedg te closingresitierll by suitable counterbalancin'g Ymeans such as aweighted arm Y .Y 34;*serrving :to holdfthe'door closed'until a suflrf; cient Weight. ofmaterialV has kfallen VonY said Ydoor 3,3 andcausesgit toppen'.V

The centralhollovvshaftrZQ be rotatedin any suitable manner,as by a largebevel gear' 35 a prime mover in any suitable'manner. Air may be forced. into, the .lower endv ofV the' shaft4 p29*, by any suitable means:V suchasa fanj38 anda con- Y i nectin'glduct 39V.A "The air 'forcedinto tlieshaft 29 will beheateda'nd may be'utiliazed to'aid the furf nace operation as rlOydischa'rgingitinto the lcompartrnents VVor zonesfabove Acertain.hea'rthsv Asuch ashearths- I5 and" IIi,` throughVY openingsflor out- -lets40.

e An importantfeatureof the apparatus relates toithe divsionlftliel .furnace I0 into an upper-2 most drying section, a central burning sectionY c V,and a lowermost section ini-which combustion` v tion.

of the gases and'other materials'is completed and Y Yoffensive odors areeliminated; VTorthis Yendrthel hearth I4 may be used to separatejthe'drying section from thercentral burning section, and the hearth I8 maybe used to separate the central burning Zone from the lowermost deodoriz'ing Vsec- In orderY to prevent the floWv of gases" Ythrough the outlets 26 ofsthe hearths I4 andi-I8, Vthere may be provided at each of these hearths a valve or feed device 4I which permits the passage Y j of thel solid. material Ybut prevent'sgrrthe passage offgases throughthe'correspondingV outlet 26.'. 115 feed typerendYY comprises 'agconveyorscrew V42 Preferably each'feed device 4 IV is ofA the screwwhich Working in a suitablecasing Vcarries ythe material, Zdropping{through 'theV correspondingV opening 25,'along for a substantialdistance to an :Y outlet Where Vit drops to a lower casing'containng'.

a conveyor screw 43 Ywhich moves the materialin..

the opposite direction-andV discharges it into the il. n

neX't'loWe'r' compartment.; The Vconveyor screwsV i suitable source of poWer. VIt will be evident that 42 and 43 maybe caused to move in oppositedi--V rections byintermeshing gears 44 mounted on. theirrespective shafts 45Vand 46. As indicated on the dravnngshaft 46'may be drivenfrom any v the material"passingthrough"the feed Ydevices orVir valves 4I serves to prevent the flow Aof gases through these devices.MVK Y f rl'heV hot gases ,ofA combustion from the burning section Aare useddirectly in drying theV material suppliedtto the ulwperrnostV or-'drying section. Y

Preferably preheated` airV is supplied Vto Vtheburning section, as already describedjrom the hollow,

Vertical shaftix29 throughoutlets 40Yin the upper 'part of the burning section. Theupperendof the shaft 29 mayzbe providedwith adamper' 41 Vto `control the passageV of air therethrough. From the. lowerzpartot theV burning Section,` hot gases." 1 fromr the ,downdrafti mayv beV passedy throughtaduct 4`8`to the upper compartment ofthe Vdrying section. Y

. *During the passageV of thegases downwardly through the drying'sectionthe gases are cooled to a substantial amountThe fcooled gases with yaporsltaken from'lthe dried materialare diseliminate noxiousodor's.

Thisr rise in temperature may be effeeted j bysupplying hot ,gases'ffror'nV the lowerrnost com- 1 chargedfrom thelowermost compartment intoa-Y i .terial' outwardly @peripheral (Sliscldla,ArgeVV V()rpe'r1ir;l} 3"s ""'ucltg which dlshalges into therlow'rermost com# v2li lor inwardlyto central discharge-openings 271,/ Y 1' ,l The hearth520,constitutingthe bottomv of: the

' iurnace'may havebut asingleroutlet 26 provided partment'of the burningvsection tojthe lowermost f sectionY of the.,deodorizing section through a duct v Y or pipe V5I! provided4 withV a damper 5I. VV,Neces- V sary additional heatingmay be provided byburning additional fuel, for example fluid fuel supplied toburners52. Y 'Y The Vburning and drying sections `arealsosup` I pliedwithburners 5.2,forruse when required.Y

, The deodorizedhot` gases from the 'deozlorizing'55-Y sectionmay bedischarged through a ue V53 con,-

nected with the-uppermost? compartmentpf the section andprovided with a suitable damper 545 As umstrated the damper'risiverueauyemovable' andisjcounterbalanced by 'aweight 55 connected with the; damper byiaiflexible member-or'rope 456Y Y Y passingfovenapulley 5 1. The'jgases may passl directly to a stack53ebut'in vieWoi the heat supplied for final burning foffthe gasesv and; Lthe consequent from 53 high temperature of the gases, it is desirable to recover some of this heat. 'Ihis may be done in any suitable manner as by using the gases to heat a waste-heat boiler 58 comprising a water drum 59, steam drums 60 and tubes 6| connecting the water drum with the steam drums. The hot gases from the flue 53 pass into the lower part of a furnace chamber 62 and between the tubes 6|, being directed to the tubes by a bridge wall 63 extending upwardly from the bottom of the chamber to the water drum 59. After passing between the tubes 6|, the gases pass through a duct 64 to a fan 65 which delivers them to the stack 53a.

The operation may be substantially as follows: In starting the apparatus material is introduced into the uppermost compartment oi the furnace, the rotation of the shaft 29 started and the fans 38 and 65 started. The burners 52 associated with the burning section may also be started as well as the burner 52 for the drying section and one or more burners 52 for the deodorizing section. Ordinarily the burner or burners 52 for the drying lsection may be turned off after the furnace is heated up, but some or all'of the burners in the burning section will be kept in use. In some-instances, the material being treated may contain enough easily combustible material of high caloric value to furnish all the necessary heat in the burning section, thus making it possible to dispense with the use of the burners in the burning sectionr after the furnace is fully heated up.

Due to the action of the fan $5` the pressure in the flue 53 will be below atmospheric pressure and there will be a down draft in the burning section from the outlets 40 in the shaftl 29 to the lowermost compartment of the section from which the hot gases may pass through the duct 48 to the upper part f the drying section or directly to the lower part of the deodorizing section through the duct 58 as controlled bythe damper 5|. From the bottom of the drying section the gases, substantially cooled in drying the materiah will ow through the duct 49 to the lower part of the deodorizing section where they will be mixed with the hot gases introduced through the duct 50 and finally burned and deodorized with the use ofthe burners 52 when necessary. In normal operation the temperature of the gases flowing through the duct 48 may be about 1200 F. and the temperature-of the gases flowing through the duct 49 may be about 350 F.

It should be noted that in the drying and burning section the flow of gases is concurrent with the ow of material and in the deodorizing section the ow vof gases is counter-current to the flow of material. It will be evident that the passing of the preheated air downwardly through the centrall burning section causes the combustion gases and vapors to pass through the low and hottest part of the burning section, thus tending to eliminate odors, and that the passing of some hot gases from the burning zone downwardly through the drying section assures the application of the greatest'amount of heat to the material at the beginning ofthe drying operation.

It should be understood that various changes may be made and that various features may be used Without others, without departing from the true scope and spirit oi the invention.

Having thus described my invention, I claim:

1. Apparatus of the, class described comprising a multiple-hearth furnace having vertically spaced hearths with outlets through which the material introduced at the top of the furnace may pass downwardly tothe lowermost hearth and i then be discharged from the furnace, means at the outlets of two hearths to prevent the passage of gases and divide the furnace into an uppermost drying section, an intermediate burning section and a lowermost section for subjecting the gases to high temperatures to completev combustion thereof and remove noxious odors before discharge from the furnace, means for supplying preheated air to the burning sec-tion, a duct conducting hot gases from the burning section to the drying section, a duct connecting the drying section with the lowermost section of the furnace, and a flue connected with said lowermost section to discharge gases of combustion from the furnace.

2. Apparatus of the class described comprising a multiple-hearth furnace having vertically spaced hearths with outlets through which the material introduced at the top of the furnace may pass downwardly to the lowermost hearth and. then be discharged from the furnace, means at the outlets of two hearths to prevent the passage of gases and divide the furnace into an uppermost drying section, an intermediate burning lsection and a lowermost sec-tion for subjecting the gases to high temperatures to complete combustion thereof and remove noxious odors before discharge from the furnace, means for supplying preheated air to the burning section, a duct conducting hot gases from the burning section to the drying section, a second duct connecting the drying section with the lowermost section of the furnace, a third duct connecting the burning section `with the lowermost section, and a ue connected vwith said lowermost section to discharge gases of combustion from the furnace.

3. Apparatus of the class Adescribed comprising a multiple-hearth furnace. having vertically. spaced hearths with outlets through which the material introduced at the top of the furnace may pass downwardly to the lowermost hearth and then be discharged from the furnace, means at the outlets of two hearths to prevent the passage of gases and divide the furnace into an uppermost Adrying section, an intermediate burning section and a lowermost section for subjecting the gases to high temperatures to complete combustion thereof and remove noxious odors before discharge from the furnace, means for supplying preheated air to the burning section, a duct conducting -hot gases from the burning section to the drying section, a duct connecting the drying section with the lowermost section of the furnace, and means for drawing the final gases of combustion from said lowermost section.

4. Apparatus of the class described comprising a multiple-hearth furnace having vertically spaced hearths with outlets through which the material introduced at the top of the furnace may pass downwardly to the lowermost hearth and then be discharged from the furnace,means at the outlets of two hearths to prevent passage of gases through these outlets and divide the furnace into an uppermost drying section, an intermediate burning section and a lowermost section for subjecting the gases to high temperatures for comai i "nace, Tand? a'riiuiiconncted with" said lowermost' 'Y section to discharge gases of .combustion from theA furnace.

Y 5; 'Apparatus of theclassdescribedrcomprising a Vmultiple'-lriearth furnacefhaving v. vertically', Vspacedheartl'is Vwithfoutlets through which the gmaterialintroduced at' the top ofthe furnacemay' pass ,downwardly Vto the ll'owermost'hearthrand then be discharged from the furnacegmeansat the outlets off4 two hearths to preventpassage of Y l ,noxious 'odors before dischargerfrom the furnace,

meansfforrsupplying preheatedairV to theupper part ofthe burning section,-a duct-conducting hot Y gasesfromrthe lowerpart ofthe burning section to the upper' ypart oftl1efdrying sectionja vsecond` VductV conductingrhot gases from the lowerpartlof vthe burning section tothe Ylowermost section, Va

third duct conductingl gases fromthe lower part ofthe 'drying Vsection to the ermost section of the'furnace, vandV a-f'flue con;

necteld withsaid lowermost section'to discharge 'gases of combustion' from the'furnace. L Y Y f 6.7'Apparartus of the class described comprising a multiple-'hearth furnace having vertically spaced hearths o material introduced at the topV of the furnace may Y pass, downwardly to "the lowermost rlie'arthand then be Vdischarged from Vthe 'furnace-rnean's' at Y the outlets of two hearths to prevent passage of` gasesY through theseY outlets and3 divide th'efurnacefY into an uppermost drying sectiongfan 'interme-4 diatefburning sectionA and a 'lowermost section Y for subjecting thefgrases rto temperatures-t VVtion Y to the V upper completegrcombustion thereof v.j andVIV removal' of before discharge from'the furnace, Y

noxious odors "means for supplyingpreheatedair to the lupper part oftherburning section, a'duct' conducting hot gases from thelower part of 'the burning sec# lower part ofthe drying section to the lower part' of the lowermost sectionof therfurnace, means for controlling the -flowofhotgases through said" secondV duct, and a flue' connected Vwith Vsaidlowrg- "ermost, section Ato discharge Ygases Ylof co'mbustio'n ,v

' f i VVNlzones,Vmeansffor 'de'taiifiing'4 the'nrate'rial'tempo-v from thje furnace.

a VVmultiple-hearth, furnace Yhaving `vertically material 'introduced at thetop of theV furnace may y pass',doiilnwardlyY to Vthe "lowerm'ost hearth and Yc Y charge from o o Y preheated airto Vthe then bedischarged froml the furnace, meansat the outlets of two hearths'lto prevent ,theV passage of gases and divide the furnace into an uppermost and a lowerm'ostfsection for subjecting the; gases Yto high' temperatures to completev combustion remove noxious odors before disthe" furnace; Vrmeans for supplying burning section, a duct conducting hot gasesmfrom. theburning section 'to thereof v and thexdrying sectlon, a duct connecting the drying section with theilowermost section of the furnace,

means including'a burner for raising the tem-w perature in said lowermost section toV complete theburning'of,the gases fromr'the other sections lower partV ofV the loW-Y v' with outlets through whichY the Y part of "their drying section,V ,asecond'rduct conducting'h'ot gases'from'the'lower'- Y "most part of 'the burning 'sectionto' the lower section, aV third duct conducting gases'fromrthe o and eiimin'atoxous odors, andrmeans 'for drawing the final gases `of combustion. fromsaid' lowermost section. i

- 8.'- Apparatus of the classdescribed comprising la -multiple-hearth furnace Ahaving a verticallyY spacedfhearths with .outlets throughrwhich the material introduced'at the topof thefurnace mayV Y pass downwardly tothe lowermost hearthanvd'vj then be discharged from'the'furnaca'meansat Y Y 'l0` Y the outlets of two hearths toprevent thepassage of gases and divide the furnace into an uppermost? Q drying section, anV intermediateburning section i Y and a lowermost section to high temperatures tofcomplete combustionv ing and part of said burning section, vsaid'hollow shaft' ducting, hot gases Y fromV :the v,lower fpartf'of: .the

`burning section VtoV the drying section; means for Yeonductng gasesV and vapors from said drying` section to said lowermost section,and'means"for heating said lower section' to completecVoxnbus-Y lprises passing the material downwardlyf:from4 for subjectingthe gases havingoutletsthroug'h whichrair is supplied to the; y

upper partzofrthe burning section, means-'con 'i il 2'5;

zone to zone through aplurality offzorfiesjY means Y for detaining'theimaterial temporarilyinv-each"Y zone', means for preventing 4the` directflowfof gases between a centralV burning Ygroup of zones; an upperidrying group offzonesV and aV lowerfdeodorizing group.ofzones,` means for passing pre'- heartedV air through the central burning'group coni Y, Y v c g terialwhile in'othis group, mean-s foripa'ssinggho't 4 Y exhaustrgases from the central group through the' currentlywith themateri'alfor burning said ma#V upper,groupzconcurrently'with'the material for" VVdrying the materiaL'means'forpassinggases'iand 1 vapors from th'e'upperg'roupjand hotgases froml the central group through the lower group courr-VA tercurrently to the material",I and me'ansforburr'iv`r` ing the gases insaid lower group therebyfelimi-'f nating odors. v

10. VVAppgatiis forl treating'."fmaterialY which; comprises means' for passing f the 'material down'* Ywardly fromrzone to' Zone througha pluralit'yof direct ilowof gases Vbetweenr a'rcentral burning groupl through theupper group/'concurrently' with' passing gases' and vapors from thei uppergroup' and' hot gasesfromfthe 'cent-rar groupthroughfitlre lower group countercurrently tof-thefmaterlal, means Vforfvarying the proportionsfoffhot' gases passing from the' central 'groupqtof the drying group-and the lower-group to control' the drying', i

rarilyf"1neach 'zoneg means 'fori preventing. the f Y' Y group of Zone/s, anrupper dryinggroupfofzones and a lower'deodor'i'zing group of Az onesymean's Y Y l Vfor'passing ypreheated air through fthe'r centrali* Abu'rningfg'ro'up concurrentlyA withf'th'e material for' Vburningvsaid material while inithisr group;means` w for passinghot' exha'lustgasesfrom'thecentralV f drying section,` an intermediateburningY sectionV 1 Y v the material'for'drying'the'materialfmeansfor l' RAIsCHii 

